Processes for preparing alkoxylated nonionic surfactants using hydrotalcite catalysts

ABSTRACT

Processes for preparing alkoxylated nonionic surfactants are disclosed, wherein a compound having at least one active hydrogen atom, a carboxylic acid ester or mixtures thereof are reacted with an alkylene oxide in the presence of a hydrotalcite catalyst to form a reaction product mixture; and the reaction product mixture is combined with an acid in at least an equimolar amount based on the amount of the catalyst present.

This invention relates to a process for the production of alkoxylatednonionic surtactants in which compounds containing active hydrogen atomsor carboxylic acid esters are reacted with alkylene oxides in thepresence of optionally modified hydrotalcite as catalyst and optionallyother selected co-catalysts and the reaction products obtained areaftertreated with acids.

An important group of nonionic surfactants are products of the additionof alkylene oxides, especially ethylene oxide and/or propylene oxide,onto compounds containing active hydrogen which are normally produced byhomogeneous catalysis in the presence of alkali metal hydroxides oralkali metal alcoholates. Products with a broad homolog distribution areobtained by the homogeneously catalyzed process. Products with a narrowhomolog distribution can be obtained by carrying out the reaction in thepresence of optionally modified hydrotalcites, for example in accordancewith DE-A-38 33 076. The alkoxylation of carboxylic acid esters alsotakes place with better results in the presence of hydrotalcites, thealkylene oxides being inserted into the carbonyl ester bond, for examplein accordance with the two patents EP-B1-0 339 425 and EP-B1-0 523 089.

However, after the actual alkoxylation using optionally modifiedhydrotalcite, separation of the catalyst from the reaction productpresents technical difficulties because the optionally modifiedhydrotalcite is generally so finely particulate that it can only befiltered through special filter candles. Unfortunately, the catalystcannot be allowed to remain in the end reaction product either becauseotherwise clouding and sedimentation can occur.

Accordingly, the problem addressed by the present invention was toprovide a process for the production of alkoxylated nonionic surfactantswhich would not have any of the disadvantages of the complex filtrationor clouding and sedimentation of the end reaction product.

BRIEF SUMMARY OF THE INVENTION

Surprisingly, the problem stated above has been solved by decomposingthe catalyst hydrotalcite and any co-catalysts present by addition ofacids after the alkoxylation rather than removing them by filtration.The invention includes the observation that the acid aftertreatmentdecomposes the hydrotalcite and any co-catalysts present into productswhich can remain in the reaction mixture without any clouding orsedimentation subsequently occurring.

Accordingly, the present invention relates to a process for theproduction of alkoxylated nonionic surfactants by reaction of compoundscontaining active hydrogen atoms or carboxylic acid esters with alkyleneoxides in the presence of optionally modified hydrotalcite as catalystand optionally co-catalysts, characterized in that at least equimolarquantities—based on hydrotalcite and optionally co-catalysts—of acidsare added after the alkoxylation.

DETAILED DESCRIPTION OF THE INVENTION

The compounds containing active hydrogen atoms may be selected, forexample, from the following classes of compounds:

a1) alcohols containing 6 to 22 carbon atoms (so-called fatty alcohols)such as, for example, caproic alcohol, caprylic alcohol, capric alcohol,lauryl alcohol, myristyl alcohol, cetyl alcohol, palmitoleyl alcohol,stearyl alcohol, isostearyl, alcohol, oleyl alcohol, elaidyl alcohol,petroselinyl alcohol, linolyl alcohol, linolenyl alcohol, ricinolylalcohol, elaeostearyl alcohol, arachyl alcohol, gadoleyl alcohol,behenyl alcohol, erucyl alcohol and the technical mixtures thereofobtained, for example, in the hydrogenation of methyl ester fractions ofnative origin or aldehydes from Roelen's oxo synthesis. Fatty alcoholscontaining 12 to 18 carbon atoms, for example technical coconut ortallow fatty alcohol cuts, are preferred.

Another group of suitable fatty alcohols are the co-called Guerbetalcohols which are produced by the alkali-catalyzed condensation of 2moles of fatty alcohol and which may contain 12 to 36 carbon atoms.

a2) Carboxylic acids containing 6 to 22 carbon atoms (so-called fattyacids) and hydroxyfatty acids such as, for example, caproic acid,caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid,palmitoleic acid, stearic acid, isostearic acid, oleic acid, elaidicacid, petroselic acid, linoleic acid, linolenic acid, ricinoleic acid,elaeostearic acid, arachic acid, gadoleic acid, behenic acid and erucicacid and the technical mixtures thereof obtained, for example, in thepressure hydrolysis of natural fats and oils. Fatty acids containing 12to 18 carbon atoms, for example technical coconut oil or tallow fattyacids, are preferred.

a3) Alkyl phenols, polyglycols, fatty amines, vicinalhydroxy/alkoxy-substituted alkanes obtainable, for example, by ringopening of epoxide compounds with alcohols or carboxylic acids andsecondary alcohols.

Within the group of compounds containing active hydrogen atoms, thealcohols or carboxylic acids containing 6 to 22 carbon atoms arepreferred.

In another embodiment of the process according to the invention,carboxylic acid esters are used as starting materials. Basically, thereare again two types of carboxylic acid esters, namely:

b1) carboxylic acid lower alkyl esters corresponding to formula (I):

 R¹CO—OR²  (I)

in which R¹CO is an aliphatic acyl group containing 6 to 22 carbon atomsand R² is a linear or branched alkyl group containing 1 to 4 carbonatoms. Typical examples are esters of caproic acid, caprylic acid,capric acid, lauric acid, myristic acid, palmitic acid, palmitoleicacid, stearic acid, isostearic acid, oleic acid, elaidic acid,petroselic acid, linoleic acid, linolenic acid, ricinoleic acid,elaeostearic acid, arachic acid, gadoleic acid, behenic acid and erucicacid and technical mixtures thereof with methanol, ethanol, propanol orbutanol. Methyl esters of fatty acids containing 12 to 18 carbon atomsand, more particularly, technical coconut oil or tallow fatty acidmethyl esters are preferably used.

b2) carboxylic acid glycerol esters corresponding to formula (II):

 in which R³CO is an aliphatic acyl group containing 6 to 22 carbonatoms and R⁴ and R⁵ independently of one another represent hydrogen orlikewise an aliphatic acyl group containing 6 to 22 carbon atoms.

Typical examples of such compounds are synthetic but preferably naturaltriglycerides, such as palm oil, palm kernel oil, coconut oil, rapeseedoil, olive oil, sunflower oil, cottonseed oil, peanut oil, linseed oil,lard oil, bovine tallow and lard. Castor oil or hydrogenated castor oilis preferably used.

In one preferred embodiment, the full esters are replaced by fatty acidpartial glycerides, more particularly monoglycerides of fatty acidscontaining 12 to 18 carbon atoms. Technical coconut oil fatty acidmonoglycerides are particularly preferred. Within the group ofcarboxylic acid esters, carboxylic acid lower alkyl esters, especiallythe methyl esters of carboxylic acids containing 6 to 22 carbon atoms,are preferred.

Optionally modified hydrotalcites are used as alkoxylation catalysts inthe process according to the invention either on their own or inadmixture with selected co-catalysts. In one embodiment of the presentinvention, optionally modified hydrotalcite is used on its own ascatalyst. Calcined or hydrophobicized hydrotalcites, as known forexample from German patent applications DE-A1 38 43 713 and DE-A1 40 10606 (Henkel), are used as modified hydrotalcites. Calcined hydrotalcitesare particularly preferred.

In another embodiment of the invention, optionally modifiedhydrotalcites and selected co-catalysts are used together asalkoxylation catalysts. Suitable co-catalysts are compounds from thegroup consisting of hydroxides, oxides and/or alkoxides of alkali metalsand/or alkaline earth metals and of alkali metal and/or alkaline earthmetal salts, tin salts and of mixed metal oxides.

Particularly suitable hydroxides of alkali metals and/or alkaline earthmetals are lithium hydroxide and/or magnesium hydroxide.

Within the group of oxides of alkali metals and/or alkaline earthmetals, the oxides of magnesium are preferred.

Preferred alkoxides of the alkali metals and/or alkaline earth metalsare those which are derived from short-chain alcohols, for example thosecontaining 1 to 8 carbon atoms, more particularly from methanol, ethanoland/or 2-ethyl hexanol. Magnesium and/or barium compounds areparticularly preferred.

Within the group of alkali metal and/or alkaline earth metal salts, themagnesium and barium salts, for example the carbonates, such asmagnesium carbonate, or the acetates, for example magnesium acetate, areparticularly important.

Mixed metal oxides are oxide compounds which contain at least twodifferent metals. One of the metals is preferably magnesium. The othermetal may be aluminium, gallium, zirconium, indium, thallium, cobalt,scandium, lanthanum and/or manganese. Magnesium/aluminium mixed oxidesare particularly preferred. The mixed oxides may be surface-modifiedwith one or more of the co-catalysts already mentioned, moreparticularly with the hydroxides and/or alkoxides of the alkali metalsand/or alkaline earth metals. Mixed metal oxides such as these and waysof modifying them are described, for example, in DE-A-44 46 064.

Magnesium oxide is a particularly preferred co-catalyst.

If the optionally modified hydrotalcites are sole catalysts, they areused in quantities of normally 0.1 to 5% by weight and preferably 0.5 to1.5% by weight, based on starting compounds (compounds containing activehydrogen or carboxylic acid esters and alkylene oxide).

If the optionally modified hydrotalcites are used together with theselected co-catalysts, they are used in quantities of normally 0.05 to2.5% by weight and more particularly 0.1 to 0.5% by weight, based on thestarting compounds. The co-catalysts may be used in quantities of 0.05to 5% by weight, preferably in quantities of 0.1 to 0.5% by weight andmore particularly in quantities of 0.1 to 0.3% by weight, based on thestarting compounds.

By virtue of the synergistic effect in catalyst activity betweenoptionally modified hydrotalcite and the co-catalysts, it is evenpossible in accordance with the invention to obtain very good resultswith a total quantity of hydrotalcite and co-catalysts below 0.5% byweight, preferably with quantities of 0.1 to 0.4% by weight and moreparticularly with quantities of 0.2 to 0.3% by weight, based on thestarting compounds.

The ratio between optionally modified hydrotalcite as catalyst andco-catalysts may vary within wide limits and is preferably between 5:1to 1:5, more preferably between 3:1 and 1:3 and most particularlybetween 2:1 and 1:2.

The reaction of the compounds containing active hydrogen atoms or thecarboxylic acid esters with the alkylene oxides may be carried out inknown manner at temperatures of 120 to 200° C. and preferably 150 to180° C. and under pressures of 1 to 5 bar. The quantity of alkyleneoxide to be added on is not critical and may amount, for example, tobetween 1 and 100, preferably to between 2 and 50 and more particularlyto between 2 and 20 moles of alkylene oxide per mole of H-activecompound or carboxylic acid ester.

Ethylene, propylene and/or butylene oxide may be used as the alkyleneoxide, ethylene oxide being preferred.

Now, it is crucial to the invention that, after the actual alkoxylation,the catalysts used, namely the optionally modified hydrotalcite on itsown or in admixture with the selected co-catalysts, are completelydecomposed in the reaction mixture obtained by the addition of acids.

Both inorganic and organic acids may be added as the acids. Suitableinorganic acids are, in particular, the mineral acids, such as sulfuricacid, hydrochloric acid and/or phosphoric acid. Suitable organic acidsare both the so-called fatty acids containing 6 to 22 carbon atoms andlower carboxylic acids containing 1 to 4 carbon atoms (only the carbonatoms of the hydrocarbon chain are counted, not the carbon atoms of thecarboxyl groups) which may optionally be additionally modified withhydroxyl groups. Preferred organic acids are the lower carboxylic acids,such as lactic acid, acetic acid and/or citric acid.

The acids are generally added as aqueous solutions, preferably as 10 to90% by weight solutions.

According to the invention, the acids are used in at least equimolarquantities, based on hydrotalcite and any co-catalysts present. Theactual quantity of acid added is of course dependent on the strength ofthe acid. Molar ratios of acid to hydrotalcite and co-catalysts, if any,of generally 1:1 to 10:1 and more particularly 1:1 to 4:1 arerecommended.

In one advantageous embodiment of the invention, the acids are added attemperatures above the melting point of the alkoxylated nonionicsurfactants, preferably at temperatures of 70 to 95° C. In practice,this is best done by keeping the reaction mixture obtained after thealkoxylation at those temperatures and adding the acid. The effect ofadding the acid is that the hydrotalcite decomposes. The decompositionproducts of the hydrotalcite are soluble in water and do not lead to anyclouding or sedimentation of the alkoxylated nonionic surfactants.Accordingly, there is no need in the process according to the inventionfor the elaborate filtration of the optionally modified hydrotalcite. Ifdesired, the acid treatment according to the invention may of course befollowed by working up of the water-soluble decomposition products ofthe hydrotalcite, for example by separation of the aqueous phasefrom theorganic phase.

The present invention also relates to the use of acids for decomposingoptionally modified hydrotalcite and co-catalysts present as catalyst inreaction mixtures of alkoxylated nonionic surfactants.

The alkoxylated nonionic surfactants obtained by the process accordingto the invention may be used without further filtration. Noprecipitation or sedimentation occurs, even after prolonged storage.Accordingly, they are suitable as nonionic surfactants for theproduction of laundry detergents, dishwashing detergents and cleanersand for the production of cleansing cosmetics, more particularly liquidproducts, such as liquid laundry detergents, hair shampoos and the like.

EXAMPLES Example 1

288.6 g (=1.35 mole) of a methyl laurate were introduced into a pressurereactor together with 5.0 g (=0.5% by weight, based on startingcompounds) of calcined hydrotalcite. The reactor was evacuated for 30minutes at 100° C. and then purged with nitrogen. 711.4 g (=12 moles) ofethylene oxide were added in portions at max. 180° C. and max. 5 barpressure. The reaction time was 150 minutes. After the alkoxylation, thereaction mixture was after-reacted for 1 hour at 120° C. and the reactorwas evacuated for another 30 minutes at 120° C.

100 g of a 10% by weight citric acid were added to this reaction mixturewith stirring at 90° C.

The calcined hydrotalcite had dissolved after stirring for 10 minutes.The reaction mixture obtained was clear in the melt.

Example 2

A mixture of 65.3 g (=0.41 mole) of a caprylic acid methyl ester and261.3 g (=1.12 mole) of a methyl ester of palm kernel oil (fatty acidchain containing 12 to 18 carbon atoms) was introduced into a pressurereactor together with 1.0 g (=0.1% by weight, based on startingcompounds) of calcined hydrotalcite and 2.0 g of magnesium oxide (=0.2%by weight, based on starting compounds). The reactor was evacuated for30 minutes at 100° C. and then purged with nitrogen. 673.4 g (=10 moles)of ethylene oxide were added in portions at max. 180° C. and max. 5 barpressure. The reaction time was 160 minutes. After the alkoxylation, thereaction mixture was after-reacted for 1 hour at 120° C. and the reactorwas evacuated for another 30 minutes at 120° C.

68.4 g of a 20% by weight acetic acid were added to this reactionmixture with stirring at 90° C. The catalyst mixture of hydrotalcite andmagnesium oxide dissolved completely in three minutes.

Example 3

638.3 g (=3,3 moles) of a C_(12/14) fatty alcohol mixture (ca. 70% byweight C₁₂ alcohol and ca. 30% by weight C₁₄ alcohol) were introducedinto a pressure reactor together with 1.0 g (=0.1% by weight, based onstarting compounds) of calcined hydrotalcite and 2.0 g of magnesiumoxide (=0.2% by weight, based on starting compounds). The reactor wasevacuated for 30 minutes at 100° C. and then purged with nitrogen. 361.7g (=8.2 moles) of ethylene oxide were added in portions at max. 180° C.and max. 5 bar pressure. The reaction time was 70 minutes. After thealkoxylation, the reaction mixture was after-reacted for 1 hour at 120°C. and the reactor was evacuated for another 30 minutes at 120° C.

An ethoxylated C_(12/14) fatty alcohol with a hydroxyl value of 179 wasobtained.

11.4 g of a 20% by weight acetic acid was added to the reaction mixtureobtained with stirring at 90° C. The hydrotalcite and the magnesiumoxide had dissolved completely after 15 minutes.

What is claimed is:
 1. A process for preparing an alkoxylated nonionicsurfactant, said process comprising: (a) reacting a starting materialselected from the group consisting of compounds having at least oneactive hydrogen atom, carboxylic acid esters and mixtures thereof withan alkylene oxide in the presence of a catalyst to form a reactionproduct mixture, wherein said catalyst comprises a hydrotalcite; and (b)combining the reaction product mixture with an acid, wherein the acid ispresent in a molar ratio to the catalyst of from 1:1 to 10:1.
 2. Theprocess according to claim 1, wherein the acid comprises a mineral acid.3. The process according to claim 2, wherein the mineral acid isselected from the group consisting of sulfuric acid, hydrochloric acid,phosphoric acid and mixtures thereof.
 4. The process according to claim1, wherein the acid comprises a carboxylic acid having from 1 to 4carbon atoms.
 5. The process according to claim 1, wherein the acidcomprises a component selected from the group consisting of lactic acid,acetic acid, citric acid and mixtures thereof.
 6. The process accordingto claim 1, wherein the catalyst further comprises a co-catalyst.
 7. Theprocess according to claim 1, wherein the acid is present in a molarratio to the catalyst of from 1:1 to 4:1.
 8. The process according toclaim 1, wherein the reaction product mixture comprising an alkoxylatednonionic surfactant is combined with the acid at a temperature above themelting point of the alkoxylated nonionic surfactant.
 9. The processaccording to claim 1, wherein the reaction product mixture is combinedwith the acid at a temperature of from about 70° C. to about 95° C. 10.The process according to claim 1, the acid comprises an aqueoussolution.
 11. The process according to claim 1, wherein the startingmaterial comprises a methyl ester of a carboxylic acid having from 6 to22 carbon atoms.
 12. A process for preparing an alkoxylated nonionicsurfactant, said process comprising: (a) reacting a carboxylic acidester with an alkylene oxide in the presence of a catalyst to form areaction product mixture, wherein said catalyst comprises ahydrotalcite; and (b) combining the reaction product mixture with anacid, said acid being present in at least an equimolar amount based onthe amount of the catalyst present.
 13. The process according to claim12, wherein the acid comprises a mineral acid.
 14. The process accordingto claim 13, wherein the mineral acid is selected from the groupconsisting of sulfuric acid, hydrochloric acid, phosphoric acid andmixtures thereof.
 15. The process according to claim 12, wherein theacid comprises a carboxylic acid having from 1 to 4 carbon atoms. 16.The process according to claim 12, wherein the acid comprises acomponent selected from the group consisting of lactic acid, aceticacid, citric acid and mixtures thereof.
 17. The process according toclaim 12, wherein the catalyst further comprises a co-catalyst.
 18. Theprocess according to claim 12, wherein the acid is present in a molarratio to the catalyst of from 1:1 to 4:1.
 19. The process according toclaim 12, wherein the reaction product mixture comprising an alkoxylatednonionic surfactant is combined with the acid at a temperature above themelting point of the alkoxylated nonionic surfactant.
 20. The processaccording to claim 12, wherein the reaction product mixture is combinedwith the acid at a temperature of from about 70° C. to about 95° C. 21.The process according to claim 12, wherein the acid comprises an aqueoussolution.
 22. The process according to claim 12, wherein the startingmaterial comprises a methyl ester of a carboxylic acid having from 6 to22 carbon atoms.
 23. A process for preparing an alkoxylated nonionicsurfactant, said process comprising: (a) reacting a starting materialselected from the group consisting of compounds having at least oneactive hydrogen atom, carboxylic acid esters and mixtures thereof withan alkylene oxide in the presence of a catalyst to form a reactionproduct mixture, wherein said catalyst comprises a hydrotalcite; and (b)combining the reaction product mixture with a mineral acid, said mineralacid being present in at least an equimolar amount based on the amountof the catalyst present.
 24. The process according to claim 23, whereinthe mineral acid is selected from the group consisting of sulfuric acid,hydrochloric acid, phosphoric acid and mixtures thereof.
 25. The processaccording to claim 23, wherein the catalyst further comprises aco-catalyst.
 26. The process according to claim 23, wherein the acid ispresent in a molar ratio to the catalyst of from 1:1 to 4:1.
 27. Theprocess according to claim 23, wherein the reaction product mixturecomprising an alkoxylated nonionic surfactant is combined with the acidat a temperature above the melting point of the alkoxylated nonionicsurfactant.
 28. The process according to claim 23, wherein the reactionproduct mixture is combined with the acid at a temperature of from about70° C. to about 95° C.
 29. The process according to claim 23, whereinthe acid comprises an aqueous solution.
 30. The process according toclaim 23, wherein the starting material comprises a methyl ester of acarboxylic acid having from 6 to 22 carbon atoms.
 31. A process forpreparing an alkoxylated nonionic surfactant, said process comprising:(a) reacting a starting material selected from the group consisting ofcompounds having at least one active hydrogen atom, carboxylic acidesters and mixtures thereof with an alkylene oxide in the presence of acatalyst system to form a reaction product mixture, wherein saidcatalyst system comprises a hydrotalcite and a co-catalyst; and (b)combining the reaction product mixture with an acid, said acid beingpresent in at least an equimolar amount based on the amount of thecatalyst present.
 32. The process according to claim 31, wherein theacid comprises a mineral acid.
 33. The process according to claim 32,wherein the mineral acid is selected from the group consisting ofsulfuric acid, hydrochloric acid, phosphoric acid and mixtures thereof.34. The process according to claim 31, wherein the acid comprises acarboxylic acid having from 1 to 4 carbon atoms.
 35. The processaccording to claim 31, wherein the acid comprises a component selectedfrom the group consisting of lactic acid, acetic acid, citric acid andmixtures thereof.
 36. The process according to claim 31, wherein theacid is present in a molar ratio to the catalyst of from 1:1 to 4:1. 37.The process according to claim 31, wherein the reaction product mixturecomprising an alkoxylated nonionic surfactant is combined with the acidat a temperature above the melting point of the alkoxylated nonionicsurfactant.
 38. The process according to claim 31, wherein the reactionproduct mixture is combined with the acid at a temperature of from about70° C. to about 95° C.
 39. The process according to claim 31, whereinthe acid comprises an aqueous solution.
 40. The process according toclaim 31, wherein the staring material comprises a methyl ester of acarboxylic acid having from 6 to 22 carbon atoms.
 41. A method oftreating a hydrotalcite catalyst-containing composition, said methodcomprising: (a) providing a mixture comprising an alkoxylated nonionicsurfactant and a hydrotalcite catalyst; and (b) combining the mixtureand an acid, wherein the acid is present in a molar ratio to thecatalyst of from 1:1 to 10:1.
 42. The method according to claim 41,wherein the mixture further comprises a co-catalyst.
 43. The methodaccording to claim 41, wherein the acid is present in a molar ratio tothe catalyst of from 1:1 to 4:1.
 44. The method according to claim 42,wherein the acid is present in a molar ratio to the combined catalystand co-catalyst of from 1:1 to 4:1.
 45. A process for preparing analkoxylated nonionic surfactant, said process comprising: (a) reacting astarting material containing a methyl ester of a carboxylic acid havingfrom 6 to 22 carbon atoms with an alkylene oxide in the presence of acatalyst to form a reaction product mixture containing an alkoxylatednonionic surfactant, wherein said catalyst comprises a hydrotalcite; and(b) combining the reaction product mixture with an acid selected fromthe group consisting of lactic acid, acetic acid, citric acid andmixtures thereof, at a temperature above the melting point of thealkoxylated nonionic surfactant; said acid being present in a molarratio to the catalyst of from 1:1 to 4:1.